Sewing machine electrical drive device

ABSTRACT

A sewing machine drive device in which a current interrupter comprising conducting rings, part of whose peripheries are insulated, and brushes, each being in contact with the periphery of the corresponding ring, is employed to make it possible to stop a sewing machine needle accurately in a desired position.

o Umted States Patent 1 1 1111 3,763,803

Mat'suda Oct. 9, 1973 SEWING MACHINE ELECTRICAL DRIVE 3,186,366 6/1965Haas et al. 112/219 A DEVICE 3,482,538 12/1969 Hayashi et al. 112/219 A[75] Inventor: Masao Matsuda, Osaka, Japan {73] Assignee: MatsushitaElectric Industrial Co. Primary Examiner Hampton Hunter Ltd" Osaka,Japan Attorney-E. F. Wenderoth et al.

[22] Filed: Nov. 27, 1972 [21] Appl. No.: 309,941 [57] ABSTRACT [52] US.Cl 112/219 A A sewing machine drive device in which a current in- [51]Int. Cl D05b 69/22 t t r comprising conducting rings, part of whose [58]Field of Search 112/219 A, 219 B, peripheries are insulated, andbrushes, each being in Ill/219 87,220 contact with the periphery of thecorresponding ring,

is employed to make it possible to stop a sewing ma- Reference-5 Citedchine needle accurately in a desired position.

UNlTED STATES PATENTS 3,477,399 11/1969 Becker et al 112/219 A 3Clalms,8Drawlng Flg I res PATENTEDUBT 91m 3,763,803

SHEET 20f 2 angle ot t he stopped position of the upper spindle FIG. 6F/GJ (b) II I o c g 5 w- 0 o o e e angle of the stopped angle of thestopped position of the upper spindle position of the upper spindle 1SEWING MACHINE ELECTRICAL DRIVE DEVICE The present invention relates tosewing machines, andmore particularly to a drive device for improvementof sewing machine functions which is provided with a control unitwhereby a sewing machine needle can be stopped in a predeterminedposition.

The sewing machine drive device of this kind usually comprises a mainand an auxiliary drive section, and provides means such an arrangementincluding a clutch, relay and the like whereby, when the sewing machineis stopped from the normal driving of the main drive section the sewingmachine upper spindle for driving the sewing machine needle isdisengaged from the main drive section and coupled to the auxiliarydrive section and rotated until the needle reaches the predeterminedstopping position. A sewing machine being an object of frequent use, itis, of course, desirable that in such machine relays, and other parts belong-lasting, as well as it being possible to stop the needle in apredetermined position. There are known drive devices to provide theabove-described function, but such conventional devices suffer from thedisadvantages that,'especially when a machine is being operated at highspeed, however careful an operator is, when he or she wishes to stop theneedle momentarily in a predetermined position, there is practicallyalways difference between the desired position and the position wherethe needle actually stops (for example,'up to 50, calculating on thebasis of angular displacement of the mechine upper spindle), or that, ifit is attempted to improve the stopping precision, chattering of relaysresults and the effective life of connecting parts is considerablylessened or low-speed rotation has to be kept at a constant speed. v

To overcome the disadvantages inherent in conventional devices, it isaccordingly an object of the present invention to make it possible tostop a sewing machine upper spindle in a predetermined position, forexample,

with a precision of within about 10 angular degrees.

It is a further object of this invention to make it possible to-maintainthe above-mentioned precision in stopping a sewing machine upper spindleregardless of the speed of low-speed operation of the sewing machine,i.e., the speed when the machine is driven by the auxiliary drivesection.

It is a further object to provide the above-described facilities whileat the same time ensuring outstandingly long service of the relays usedin the control unit.

According to one preferred embodiment of the present invention, a sewingmachine electrical drive device is shown as generally comprising a maindrive unit, a secondary drive unit that operates at reduced speed, abrake unit that controls the secondary drive unit, a clutch assembly forselective engagement with the main or secondary drive unit to drive asewing machine upper spindle, a switch that is closed when said clutchassembly is engaged with the main drive unit and open when the clutchassembly is disengaged from the main drive unit and engaged with thesecondary drive unit, a relay possessing a holding contact and contactswhich control the above-mentioned brake unit, and a current interrupterfixedly mounted on the sewing machine upper spindle and comprisingconducting rings, part of whose peripheries are non-conducting and intotwo of which grooves are cut at the respective non-conductingperipheries the length of the arc lying between the grooves in one ringbeing greater than that between the grooves in the other, and brusheswhich contact the said'conductin'g rings, wherein the said relay isbrought into connection with an electrical power source through theaction of the said switch and through the said brushes in contact withsaid conducting rings and a series circuit in connection with theabove-mentioned holding contact.

In the arrangement of a sewing machine drive device as hereinbeforedescribed, a current interrupter comprising conducting rings, part ofwhose peripheries are insulated, and brushes, each being in contact withthe periphery of the corresponding ring, makes it possible to stop asewing machine needle accurately in a desired position. Since it isensured that the sewing machine upper spindle is always stopped from thereduced speed of the secondary drive unit by the. relay controlled bythe current interrupter of three rings contacted each other in a line attheir peripheries part of which are non-conducting, a first ring ofwhich contacts a brush in connection with the power source, a secondring of which contacts a brush in connection with therelay through theholding contact,.and a third ring of which contacts a brush inconnection with the relay.

These and other objects and features of the present invention willbecome apparent from the following description taken in conjunction withone preferred form of embodiment thereof shown in the accompanyingdrawings, in which;

FIG. 1 is a schematic front view of the sewing machine associated withan electrical drive device embodying the present invention, portions ofwhich are broken away for the purpose of illustration of variouscomponent parts disposed therein,

FIG. 2, (a) and (b), is a control circuit diagram employed in the drivedevice of FIG. 1,

FIG. 3 is an exploded schematic perspective view, on an enlarged scale,of the association among essential parts of the drive device of FIG. 1,

FIG. 4 is a time chart illustrating operative stages of the drivedeviceof the present invention,

FIG. 5 is an explanetory graph illustrating stopping point distributionof the sewing machine spindle driven by the drive device of the presentinvention,

FIG. 6 is a similar view to FIG. 5 but using a conventional drivedevice, and I FIG. 7 is a similar view to FIG. 6 but using anotherconventional drive device.

Before the description of the present invention proceeds, it is to benoted that like parts are designated by the like reference numeralsthroughout the several views of the accompanying drawings. It is furtherto be noted that, for the sake of brevity, the description of thepresent invention will be hereinafter made in comparison with theconventional drive device used in a sewing machine.

Referring first-to FIGS. 1 to 3, a sewing machine table 1 is supportingthereon a sewing machine headstock 3 provided with an upper spindle 2 onwhich is mounted a pully 4 and a current interrupter S comprising threerings 5, 6 and 7 each being in sliding contact with the correspondingfixed brushes 8, 9 and 10, which detects the angular position of theupper spindle 2 in connection with the stopping position of a sewingmachine needle 30. The sewing machine drive unit associated with atreadle 25 is mounted below the sewing machine table 1 by conventionalmeans such as a bolt and the like and comprises a main motor 13 whichprovides direct drive to a fly-wheel 12, on which is fixedly mounted aclutch plate 11 for high-speed operation, a secondary motor 18, whoseshaft is in connection at one end with a direct current electromagneticbrake unit 17 and at the other end with a worm 16, which always engagesa worm gear mounted on a clutch plate 14 for low-speed operation, and aclutch including the pair of clutch plates l1, l4 and a rotatory disc21, which, through connection with a clutch shaft on which is mounted amotor pulley 22, and cooperative action of a lever 19, is selectivelyshifting in the direction of the clutch shaft 20 to engage with thehighspeed clutch plate 11 or the low-speed clutch plate 14. The sewingmachine upper spindle 2 is driven by a belt 23 around the motor pulley22 of the clutch shaft 20 so that, when the rotatory disc 21 is infrictional engagement with the high-speed clutch plate 11, the upperspindle 2 is driven fast, and when it engages the lowspeed clutch 14,the upper spindle 2 is driven by the secondary motor 18 acting throughthe worm l6 and the worm gear 15.and is slowed to low-speed operation.The lever 19 is operated to shift it in the direction of the clutchshaft 20 by means of the treadle as well known in the prior art, towhich it is connected by a rod 24 and through a'switch 26 ofconventional construction, which is always opened and is closed upon thetreadle 25 being pressed down, whereupon the lever 19 causes therotatory disc 21 to engage the high-speed clutch plate 11.

The current interrupter S fixedly provided on the upper spindle 2comprises a metal ring 7, part of whose periphery faced to the nextmetal ring 6 is insulated by an insulator 40, around a central insulatorportion 38 to be mounted on the upper spindle 2, the metal ring 6, partof whose periphery faced to the next metal ring 5 is similarly insulatedby an insulator 41, around a central insulator portion 38 to be mountedon the upper spindle 2 and into which a pair of grooves 27, 28 are cutat both ends of the insulator 41 at an angle a with respect to oneanother to form an insulation portion E, and the metal ring 5, part ofwhose periphery faced to the last metal ring 6 is also insulated by aninsulator 42, around the central insulator portion 38 to be mounted onthe upper spindle 2 and into which a pair of grooves 29, 30 are cut atboth sides of the insulator 42 at an angle B with respect to one anotherto form an insulation portion F, it being essential that the metal ring5 be provided with the insulation portion F of the angle B correspondingto the amount of ranges in which position the sewing machine spindlecan. be stopped and, for example, being 10 angular degrees greater thanthe angle a of the metal ring 6 so that the insulation portion F isextended a small amount of itself beyond the both ends of the insulationportion E when the set of metal rings 5, 6, 7 are fixedly mounted in aline on the upper spindle 2 and pressure engaged to one another as shownin FIG. 1. In this arrangement of the current interrupter S, theconduction portions B, C, D, of the three metal rings provide a path forcurrent as a unit, but the insulation portions E and F of the two metalrings 5, 6 being completely isolated electrically, no current flow ispossible, of course, between E and F, nor between E and B, C, D, or Fand B, C, D. In other words, the brush 10 does not conducted to theother brushes 8, 9 when they are simultaneously in contact with therespective insulators E, F of the metal rings 6,

5 within the range of angle a, but does conducted to the one brush 9when the brush 9 is not in contact with the insulator E of the metalring 6 while the brush 9 is not contact with the insulator F of themetal ring 5 within the range of angle (B-a), and dose conducted to theother brushes 8, 9 when they are simultaneously in contact with therespective metal rings 6, 5 excluding the insulation portions thereofwithin the range of angle (360B).

Below follows a description of the device of the present invention withreference to FIGS. 1 to 4. The control electric circuit of the sewingmachine drive device mentioned hereinbefore is D.C. operated byconventional means, the necessary DC. voltage being obtained fromrectified main motor 13 alternating current taken through an isolationtransformer 31 and a rectifier 32, whose construction is that of aconventional full-wave bridge rectifier. In the circuit there isprovided a relay 33 having a holding contact 37 and makeor-breakcontacts 34, 35, 36, in which a pair of contacts 35, 36 form a supplycircuit to the secondary motor 18 as shown in FIG. 2 while the contact37 is in connection with the brush 9 of the metal ring 6 and the contact34 is in connection with a direct current elec tromagnetic brake coil17'. Upon excitation of the relay 33, the magnetic field in the directcurrent electromagnetic brake coil 17' demagnetizes, and the contacts35, 36 close the supply circuit to the secondary motor 18, which causesrotation of the worm 16, and hence of the low-speed clutch plate 14.Conversely, upon demagnetization of the magnetic field of the relay 33,the supply circuit to the secondary motor 18 is cut, the direct currentelectromagnetic brake coil 17' is energized, and the secondary motor 18,and hence the low-speed clutch plate 14, is stopped. The metal ring 7 isin permanent connection with the positive side of the rectifier 32through the brush l0, and voltage impressed on the portion B of themetal ring 7 is likewise impressed on the portions C, D of the metalrings 6, 5 respectively, from where voltage taken out through the brush9 being impressed on a circuit point 101 of the relay 33 through theholding contact 37, and that taken out through the brush 8 beingimpressed on the. circuit point 101 directly. A resistor 39 and a diode43 form a series circuit connected in parallel to the relay 33 andconnected in series to the switch 26, which series circuit can also besuitably composed of a capacitor and resistor, varistor, or any othersimilar surge absorption circuit.

The sewing machine is started by depression of the treadle 25 by theoperator, whereupon, through the action of the lever 19, the rotary disc21 is brought into frictional engagement with the high-speed clutchplate 11 being rotated by the main motor 13 which is driven by a mainswitch (not shown in figure) as well known in conventional method, andthe switch 26 is closed at the same time. As the switch 26 is closed,voltage from the rectifier 32 is applied to the relay 33 through lines102 of the switch 26 and 103 of the relay 33, and the relay 33 isexcited so that the direct current electromagnetic brake coil 17' isdemagnetized and the contacts 35, 36 close the supply circuit to thesecondary motor 18, which therefore becomes operative. At the same time,the voltage built-up in the relay 33 closed the holding contact 37, sothat even if the switch 26 is turned off by restoration of the treadle25 to the original position both circuits one of which including theline 102, brush 10, metal ring 7, metal ring 6, brush 9, holding contact37, circuit point 101 and relay 33, and the other of which including theline 102, brush 10, metal ring 7, metal ring 6, metal ring 5, brush 8,circuit point 101 and relay 33 are maintained automatically held toclose of themselves. When the treadle 25 returns to its original.position, the rotatory disc 21 is released from engagement with thehigh-speed clutch plate I1 and the switch 26 is opened. Although themagnetic field of the relay 33 is demagnetized upon opening of the abovementioned circuits by the complete contact between the insulator 41 ofthe metal ring 6 and the brush 8, demagnetization of the magnetic ,fieldin the relay 33 is not, however, immediate, but is delayed due to thereasons that during high-speed operation of the sewing machine byclosing the holding contact 37 in parallel with the switch ,26 durationof contact between the insulation portion E of the metal ring 6 and thebrush 9 is extremely brief because of the high-speed rotation of themetal ring 6 and of the small angle a of the insulator 41 mounted on themetal ring 6, the response of the relay 33 is generally poor, and

the series circuit 39, 43 of surge absorption is in connection with therelay 33. Hence, the relay 33 is enabled to be self-closing until thesewing machine upper spindle 2'reaches a certian rotatory speed N, whichdepends on thedemagnetization time of the relay 33 and the size of theangle a enclosed by the insulation portion E of the metal ring 6. Whenthe rotatory speed of the upper spindle 2 is less than a certain speed Nand the contact time between the brush 9 and the insulation portion E ofthe metal ring 6 is enough for demagnetizing the magnetic-field of therelay 33 so that the relay 33 can no longer maintain excitation for asufficient length of time and its magnetic field collapses completely,whereupon the contact 37 is opened, contacts 35, 36 are opened, thuscutting supply of current to the secondary motor 18, the contact 34 isclosed, thus voltage is applied to the direct current electromagneticbrake coil 17, and the secondary motor 18 is stopped, thus stopping thelow-speed clutch plate 14 and the rotatory disc 21 with which itisengaged, and hence the upper spindle 2. Accordingly, the sewingmachine needle is stopped within a predetermined position in accordancewith the stopped positionof the upper spindle 2 because the upperspindle 2 is stopped in such a manner that the metal ring 5 mounted onthe upper spindle 2 is stopped in contact with the brush 8 at itsinsulation portion F within the range of angle [3 after rotation speedof the upper spindle 2 is exactly lowered to the certain speed N, byarrangement of the metal ring 6, brush 9 and holding contact 37 asmentioned hereinafter with reference to FIGS. 4 to 7.

In FIG. 4 shown relation between the speed of the sewing machine upperspindle 2 and the time of operation, at the time from starting of thesewing machine by depression of the treadle 25 the main motor 13 isreached to the full speed to rotate the upper spindle 2 through theclutch plate 11 and the rotatory disc 21, and the secondary motor 18 isreached to the full speed at the time I, from the simultaneous closingof the switch 26. In connection of the high speed N, rotation of theupper spindle 2 driven by the main motor 13, if the treadle 25 isreturned to its original position at the time t, the rotatory disc 21 isdisengaged from the highspeed clutch plate 11 and engages the low-speedclutch plate 14 by the lever 19 and the upper spindle 2 falls rapidlyfrom the high-speed N, to the low-speed N of the secondary motor 18.During this fall in speed of the upper spindle 2, if the brush 9 isbrought into contact with the Insulation portion E of the metal ring 6in the interval a to b shown in FIG. ,4 between the middlespeed N andthe low-speed N; which can be obtained the enough time for opening therelay 33, the upper spindle 2 goes beyond the low-speed rotation of thesecondary motor 18 and is stopped at the point c shown in FIG. 4.However, the stopped position of the upper spindle 2 at point 0 oftenlies within the hatched portion X of FIG. 6 beyond the predeterminedarea Y defined as an angular range deviated the same amounts in thenegative and positive direction with respect to the desired stopposition of the sewing machine needle, since the speed for opening therelay 33 in the condition of contacting the brush 9 with the insulationportion E of the matal ring 6 is relatively high and varies at randam,for example, if the speed as it opened the relay 33 is near to themiddle-speed N the stopped position of the upper spindle 2 is far fromthe predetermined area. FIGS. 5 to 7 respectively show curves of theangular deviations with respect to the stopped position of the upperspindle 2, each in which an abscissa expresses the frequency ofoccurrence in connection with the stopped position of the upper spindle2 and an ordinate defines the positive or negative angle with respect toa standard point of the upper spindle 2, the spindle of FIG. 5 beingemployed three metal rings 5 to 7 with the holding contact 37 inaccordance with the present i nvention while the other spindles of FIGS.6 and 7 are employed two metal rings 5 and 7, or 6 and 7 and aresometimes stopped beyond the predetermined area relating to the desiredstop position of the sewing ma- .chine needle. It is to be noted thatthe middle speed N,

which settles the upper limit for closing the relay 33 is necessary toset .a speed much higher than the lowspeed N of the secondary motor 18since if the middlespeed is equal or near to the low-speed there occursto make it impossible to operate the secondary motor by the relay 33which is maintained to keep its closing without reliability in somecases. In addition, the brush 9 is in contact with the insulationportion E of the metal ring 6 in the interval b to f of FIG 4 inlow-speed N of the secondary motor 18 the upper spindle 2 is stopped atpoint e in FIG. 4 of which the angular deviation lies within thepredetermined area of the central distribution curve of FIG. 6, sincethe speed of demagnetizing in the relay 33 is always even. However, whenthe upper spindle 2 has two metal rings 6 and 7 with the holding contact37 of'the relay 33 except for the metal ring 5, the stopped position ofthe upper spindle 2 does not ensure to put into the predetermined areaas shown in FIG. 6, so that the present invention is provided a sewingmachine electrical drive device in which the upper spindle has threemetal rings 5, 6 and 7 including the metal ring 5 in contact with thebrush 8 connected directly with the relay 33 so as to eliminate thedisadpoint of the upper spindle 2 falls within the hatched, tailingportion shown in FIG. 6 beyond the predetermined area. By thisarrangement, when the brush 8 comes into contact with the connectionportion D of the metal ring 5 beyondits insulationzportion Fcorresponding to the insulation portion E of the next metal ring 6 therelay 33 is again energized through the three metal rings 5, 6 and 7 andthe secondary motor 518 started, under which conditions the upperspindle 2 is again driven to rotate at the low-speed N by the secondarymotor 18 as following the dotted line to h of FIG. 4 and, whenthe brush8 is again brough into contact with the insulation portion F of themetal ring 5 at point g in 'FIG. 4 and the secondary motor 18 is stoppedby opening the relay 33, is stopped within the predetermined area atpoint d-.'in FIG. 4. Accordingly, with this arrangement it is ensurethat the stopping point of the upper spindle 2 alway lies within thepredetermined area Y of the central distribution curve of FIG. 5 sinceit can eliminate the disadvantages of the FIG. 6 by the provision of themetal ring 5 having the insulation portion F of which distance ismorewider than that of the corresponding insulation portion E of themetal rim 6 'and the brush 8 being in contact with the metal ring 5 andin connection with the relay 33. Thus, by suitable positioning of theupper spindle 2, a sewing machine drive unit of extremely high precisionis obtained. Moreover, there are known conventional devices which do notpossess the metal ring 6 and the holding contact 37, but with the otherrings 5 and 7 there is no guarantee that the stopping point of the upperspindle 2 lies within the predetermined area of the distribution curveof FIG. 5, but rather the distributionis always as shown in FIG. 7 andvaries in accordance with the middle speed N depending upon thecharacteristic of the relay 33. When the middle-speed N is larger thanthe low speed N enough to step the spindle 2, there is a strong tendencyfor producing chattering of the relay 33, which considerably impairs thelength of the service-life of the relay 33, and the upper spindle 2 isoften stopped beyond the predetermined area as shown with an area 2 inFIG. 7, while, when the middle-speed N is small sufficient to eliminatethe chattering of the relay 33, the upper spindle is stopped within anarea Y in FIG. 7. In other words, theformer is one case in whichcondition the low-speed N is much smaller than the middle-speed N whilethe latter is the other case in which condition the middle-speed N islarge than that of the former and near to the middle-speed N This isbecause'that the sewing machine is generally driven either at high-speedabout 6,000 r.p.m. or at low-speed about 3,000 r.p.m. by the operatorselection and, accordingly, the low-speed N lies on either high-speed orlow-speed. The area Z of FIG. 7 shows the frequency of occurrence whenthe sewing machine proved compared with conventional devices, and

is driven at low-speed, and the area Y of FIG. 7 shows which eliminatesrelay chattering, thus improving relay service-life, and in which,moreover, precision does not depend on the speed of operation of asewing machine, the device of the present invention thus being of greatpractical advantage in sewing machine operation.

Although the present invention has been fully described with referenceto the accompanying drawings in connection with the preferred embodimentthereof, various changes and modifications are apparent to those skilledin the art. Therefore, the present invention is not to be limitedthereby and such change and modifications should be construed asincluded within the scope of the present invention unless otherwise theydepart therefrom.

What is claimed is:

1. A sewing machine electrical drive device comprising a main driveunit, a secondary drive unit that operates at reduced speed, a brakeunit that controls the secondary drive unit, a clutch assembly forselective engagement with the main or secondary drive unit to drive asewing machine upper spindle, a switch that is closed when said clutchassembly is engaged with the main drive unit and open when the clutchassembly is disengaged from the main drive unit and engaged with thesecondary drive unit, a relay possessing a holding contact and contactswhich control the abovementioned brake unit, and a current interrupterfixedly mounted on the sewing machine upper spindle and comprisingconducting rings, part of whose peripheries are non-conducting and intotwo of which grooves are cut at the respective non-conductingperipheries the length of the arc lying between the grooves in one ringbeing greater than that between the grooves in the other, and brusheswhich contact the said conducting rings, wherein the said relay isbrought into connection with an electrical power source through theaction of the said switch and through the said brushes in contact withsaid conducting rings and a series circuitin connection with theabove-mentioned holding contact.

2 A sewing machine electrical drive as claimed in claim 1, wherein thesaid current interrupter comprised a first metallic ring part of whoseperiphery is insulated by an insulator material around a central portioncomposed of an insulator material, a second metallic ring part of whoseperiphery is insulated by an insulator material around a central portioncomposed of an insulator material, said grooves being cut at theinsulation portion at a distance from one'another into the centralportion, and a third metallic ring part of whose periphery is insulatedby an insulator material around a central portion composed of aninsulator material, said grooves being cut at the insulation portion ata distance from one another into the control portion, the distance ofthe third ring being greater than the distance of the second ring, thesaid three metallic rings being brought together by pressure engagementin which configuration the portions between grooves of the said tworings form insulated portions, the first ring contacting with a brushconnected to the power source, the second ring contacting with a brushconnected to the relay through the holding contact, and the third ringcontacting with a brush connected to the relay.

3. A sewing machine electrical drive device as claimed in claim 1,wherein the said relay contacts function to actuate the said secondarymotor upon energization of the said relay and to actuate the said brakeunit uponde-energization of the relay.

1. A sewing machine electrical drive device comprising a main driveunit, a secondary drive unit that operates at reduced speed, a brakeunit that controls the secondary drive unit, a clutch assembly forselective engagement with the main or secondary drive unit to drive asewing machine upper spindle, a switch that is closed when said clutchassembly is engaged with the main drive unit and open when the clutchassembly is disengaged from the main drive unit and engaged with thesecondary drive unit, a relay possessing a holding contact and contactswhich control the above-mentioned brake unit, and a current interrupterfixedly mounted on the sewing machine upper spindle and comprisingconducting rings, part of whose peripheries are non-conducting and intotwo of which grooves are cut at the respective non-conductingperipheries the length of the arc lying between the grooves in one ringbeing greater than that between the grooves in the other, and brusheswhich contact the said conducting rings, wherein the said relay isbrought into connection with an electrical power source through theaction of the said switch and through tHe said brushes in contact withsaid conducting rings and a series circuit in connection with theabove-mentioned holding contact.
 2. A sewing machine electrical drive asclaimed in claim 1, wherein the said current interrupter comprised afirst metallic ring part of whose periphery is insulated by an insulatormaterial around a central portion composed of an insulator material, asecond metallic ring part of whose periphery is insulated by aninsulator material around a central portion composed of an insulatormaterial, said grooves being cut at the insulation portion at a distancefrom one another into the central portion, and a third metallic ringpart of whose periphery is insulated by an insulator material around acentral portion composed of an insulator material, said grooves beingcut at the insulation portion at a distance from one another into thecontrol portion, the distance of the third ring being greater than thedistance of the second ring, the said three metallic rings being broughttogether by pressure engagement in which configuration the portionsbetween grooves of the said two rings form insulated portions, the firstring contacting with a brush connected to the power source, the secondring contacting with a brush connected to the relay through the holdingcontact, and the third ring contacting with a brush connected to therelay.
 3. A sewing machine electrical drive device as claimed in claim1, wherein the said relay contacts function to actuate the saidsecondary motor upon energization of the said relay and to actuate thesaid brake unit upon de-energization of the relay.